Suppressive activity of quercetin on the production of eosinophil chemoattractants from eosinophils in vitro.

Quercetin, a flavonoid found in a wide variety of plants, has been studied for possible health benefits, and it has been found to have potent anti-oxidant, anti-viral and anticancer effects. Although quercetin is also reported to act as an antihistamine and an anti-inflammatory through the suppression of mast cell activation, the influence of quercetin on eosinophil activation is not fully understood. The present study, therefore, was undertaken to examine the influence of quercetin on eosinophil activation, especially chemokine production by using an in vitro cell culture technique. Eosinophils (5×10(5) cells/ml) obtained from Mesocestoides corti-infected mice were stimulated with 200 ng/ml stem cell factor in the presence of different concentrations of quercetin for 24 h. Chemokine, eotaxin, regulated on activation normal T cell expressed and secreted and macrophage inflammatory protein-1β, levels in culture supernatants were examined by enzyme-linked immunosorbent assay (ELISA). We also examined the influence of quercetin on chemokine mRNA expression and transcription factor, nuclear factor kappa B and activator protein 1, activation by real-time reverse transcription polymerase chain reaction and ELISA, respectively. Treatment of eosinophils with quercetin at more than 4.5 μM caused a significant decrease in chemokine levels in culture supernatants. Quercetin also suppressed transcription factor activation in 4 h-cultured cells and mRNA expression of chemokine in 12 h-cultured cells, which were increased by stem cell factor stimulation. These results may suggest that quercetin inhibits eosinophil activation, especially chemokine production, and results in inhibition of the development of eosinophilic inflammatory responses.